Induction heating of canned goods



July 19, 1960 H. A. MESSNER ET AL mnucnou HEATING 0F CANNED GOODS Filed Sept. 11, 1957 INVENTORS HARLAN A, MESSNER RRY B. OSBORNJR.

ATTORNEY States PatcntOfiEice 2,945,935 INDUCTION HEATING-OF CANNED GOODS Harlan A, Mess ner, San Marino, Califg, andHarry B. Osborn, .Jr., Cleveland; Ohio, assignors to The Ohio Crankshaft Company, Cleveland, Ohio, a corporation r oh'ier Filed Sept. 11,1957, Ser. No. 683,368

teatime. (Cl:"2'19'-10.41)

The present invention relates' 'to the art of induction heating and more" particularly 'to the simultaneous induction'heatingof aplu'ra'lity of oann'ed'g'oods' in a carton.

The invention is particularly adaptable for use in the food "indnstrywhe reimgoods inmetal cans are stored in carton'srin 'co'ol 'storag'e placessuchas'cold storage rooms, refrigerators, deep freezes, and the like; It is understood, h wever; that theinvention maybe used in conneetion with cannedgoods other'th'an'thoseused' in the food industry "or that it may used whenever canned goods are'm'oyed'to 'a 'place havin'g a dew point below the temperatur'eof the plac'e from which moved. Dew pointmaybe defined'asthe temperature at which moisture entrained in air" begins to condense out and varies: proportionally to the amount of moisture entrained. It'may'otherWisebe-defined as the'temperature where the relative humidity reaches 100%. I

Generally, ca'ns arepa'ckag'edwith'several rows or a plurality of. cans in eacli'carton'; Usually the cans have a paper or otheridentifi'cation wrapper on them and the cartons are constructed from cardboard.

Iti is well known" that when canned goods or similar articles are" moved from an area or place maintained at places in homes; stores, orthe like.

The moisture condensing; on the cans discolors the wrap ers ay ruin-the carton; and also strains and discolors the cannedgoods; alongwith the rusting away of thecan; This discoloration and rusting is extremely detrimental; especiallyjin' the food industry, wherein peopledo not purchasecanned' food if there is anyrust or discoloration on the surface of the can. Furthermore, if the rusting progresses tothe point where it eats through the wall of" the can, any food contained therein would becontaminated andinjurious to the health.

Although these problems have confronted industry for a longtime; a praetie'al' solution to the'problem of. preventing the condensation of water on the canned goods was unknown prior to the present invention. Various 31ttempts have been made in an effort to heat canned goods, to de-humidify the atmosphere, and to use moisture-proof cartons. Eachofthese methods raised problems either from the extra handlingof the canned goods, or the extra cost of materialsr 7 I s The present invention contemplates the solvingf'ofi these and other" problems by devising a method and' apparat-us wherein the canned goods are heated to the temperature of or above the dew point of the surrounding atmosphere without removing the cans from the cartons and without opening the cartons.

In accordance with the present invention, a carton containing a plurality of or several rows of cans of goods is Patented July 19, 1960 2. subjected to an alternating magnetic field:capable of inducing electrical heating currents mail of the cans in the canton simultaneously to heat the cans andprevent condensation of moisture thereon; I

Further, in accordance with the'invention, the mag: netic field is established by, an' induction heating coil energized at a frequency providing induced currents in all of thecans simultaneously andat a'frequency in which the reference-depth of'the induced'current is less than the thickness of the wall of any one 'of the cans.

In view of the foregoingrproblems, and the'present solution of those problems, it is apparent that one of the objects of the present invention is to prevent rusting or dis coloration of cans and condensationofmoisture thereon when cartons ofcans are removed from cold storage or the like to higher temperature atmospherenini a manner which is economical and practical. i

A further object of'the invention is;to simultaneously heat all-of the-cans in a carton to a temperature above the dewpoint of the atmosphere or toa temperature the same as the temperature of' theatrnosphere inwhicli the carton is placed without removing the cans fromthe carton or opehingthecarton;

Other objects of the invention will-become apparent from the following description of. a specific example or embodiment of theinvention whentaken. conjunction with the accompanying drawing illustrating .tliatrspecific. embodiment in'elevational plan view; v

The attached drawing illustrates, as aspecific embodiment of the invention; a-carton10 containing a plurality of cans 1-1- cooperatively arranged with an-induction coil ll-for the purposeof heating'the cans t'oa temperature above the dew point ofthe surrounding "air or atmosphere.

The induction coil 12- is connected'toa suitable generator 13 or other source ofIalter natingcurrent so that it will induce heating currents inall of the cans 11 in the carton '10 simultaneously. I I

The cartonsare usually constructed from'cardboard'or any other suitable material and areofa' size and shape, so'thatthey Will-hold a plurality of cans 1'1; Each can 11 is constructed from sheet'materialwhich is: electrically conductive and is adapted to have current; induced therein for heating the sheet material. In thisdnstance', the carton 10 is illustrated asenc'losing-9 cans, however, it is understood that the'ex actnumber of, cans: is not in1- portant to the invention and that there may be one or more cans in the carton. It is further understood that these cans may be positioned 'in rows as illustratedso'that some of the cans are next adjacentoutside walls ofjthe' cartongand some of the cans are separatedpr spaced" from the outside Wall by other cans.- cans-have a wall thickness which is relatively-thin;

In carrying out the present invention, a cart0n10 containmg a plurality or several rows of cans 11 is passed through a magnetic field established by the inductioncoil 12 immediately after the carton is removed from cold storage or such other similar cool place and into air'or atmosphere ofa higher temperature. The induction coil 12 causes magnetic fiuxto pass through the entire carton 1 0 and all of the cans 11 contained therein so that induction heating currents are induced' simultaneously in all of the cans in the canton. The cartons may be passed; through the coil 12 and supported therein by means of a table such as table 14, or they may be continuously moved through the coil by means of conveyor belt-or other suitable means commonly knownin the materials handling fields.

Alternating currents from the power source 13 flow through the coil 12 and create an alternating magnetic flux field on the inside of the coil 12, which flux passes through the paper of the carton without interference. This flux also threads into the metal of the cans and in- Generally; the.

duces currents to flow therein of a frequency equal to that of the power source. These currents heat the metal of the can in accordance with known principles. This heat is conducted inwardly through thecontentsof the;

can ,and, if the heating were containued for a long enough ti e, the entire contents of the can could' be raised to any desired temperature;

c The total amount of heat supplied to the cans, in accordance with the invention, must be sufficient so that after the cans are removed from the coil 12, they will be at atemperature equal to, or in excess of, the dew temperature of the surrounding atmosphere. Obviously, this dew temperature will vary dependent upon the amount of moisture entrained in the air which, in turn will be dependent upon conditions beyond the scope of the invention- Thus, in the summertime, when the relative humidity is high, the dew point is high and the final temperature of the cans must also be high. In the wintertime, however, the relative humidity of the air inside ofheated buildings is relatively low and the final temperature which the cans must-reach can be lower. Suffice it to say that if an amount of heat is supplied to the cans so that the final temperature will be equal to the surrounding room temperature, no problem of condensation will result...

The total amount of heat supplied to each can will depend upon the-rate of heating and the length of time of heating. Thus, the rate of heating can be relatively low and the heat supplied for relatively long periods of time. Alternatively, the rate of heating can be high and the length of time of heating held relatively short. Normally, the-rate of heating will be as high as is possible without overheatingthe surface of the can. Thus, if the rate of heating is too high, the surface of the can can be raised to temperatures suflicient to either melt the solder or to scorch the label, even though the contents of the can have not been appreciably heated. Thus, the rate of heat conduction through the contents is ordinarily much slower than through metal, and it is possible to have the outer surface of the contents at the boiling temperature while having the inner core of the contents still frozen. Obviously, if a can in this condition were then set aside, the heat on the external portions of the contents would be conducted inwardly and if the total amount of heat supplied were proper, the final temperature of the can and contents would be as desired.

LAs the rate of heating will vary dependent upon the contents of the can and their condition before being placed in the coil 12, it is impossible to specify rates of heating. 7

The coil 12 may be of any desired shape, but preferably has a cross-sectional shape approximately the same as the cross sectiona1 shape of a carton. The ratio of the cross-sectional area of the coil 12 to the ratio of the cross-sectional area of a carton should be kept as small as possible.

The frequency of the power source 13 will depend, to some extent, upon whether the cartons contain several layers of cans on the inside, or whether there is only a single layer. Thus, if a single layer of cans is employed, the 'fiequency is relatively unimportant but somewhat better electrical couplings to the cans can be obtained by using frequencies on the order of 3,000 to 10,000 cycles per second. However, when multiple layers of cans are employed, the frequency is preferably held relatively low, for example, to 60 cycles per second. With such a frequency, the reference depth of flux penetration is greater than the thickness of the metal of the can. Thus, theflux, or at least portions thereof, will pass through the can and will act on cans in the center of the carton, thereby uniformly heating all the cans in the carton at one time.

The invention has been illustrated in the drawings somewhat schematically. Obviously, mechanical or automated means may be employed for moving the cartons through the coil 12, or the coil 1 2 may be made 7 portable and moved from one carton to the other}- In using the invention, the desired final temperature to which the cans must be raised must be determined by determining the dew point of, the surrounding atmosphere into which the cans will move followingtheir re moval from the cold storage area. The amount of heat to be supplied to each can must also be determined, taking into consideration the final temperature and the temperature of the cold storage area. The amount of energy supplied to the coil 12 should then be made as high as possible while preventing the overheating effects above referred to; taking into account the rate of energy supplied to the coil 12, the time of heating may then be determined. i a

. Using the invention, the problems of preventing the condensation of moisture on cans as they are removed from cold storage area, together with the resultthereof, namely, discoloration, rust, or the like, are obviated, and it is possible :to prevent this condensation or moisture while the cans are still .within their original carton.

It will be appreciated that insome instances, the invention could be employed to heat the cans individually as they move from a storage area into a shipping carton.

The invention has'been described with-reference to a preferred embodiment. Modifications, and alterations will occur to others upon a reading and understanding of this specification, and it is our intention to include all such modifications and alterations insofar as they come within the scope of the present invention. i l

Having thus described our invention, we claim:

1. A method of preventing moisture'condensation on a plurality of thin-walled cans contained in a carton which has been in cold storage at a temperature substantially below the temperature of -a new environment where the cans are to be stored, said method comprising the steps, of: removing the carton with the cans thereinfrom cold storage to a new environment having a temperature substantially higher than that of the cold storage environment; and, while the thin-walled cams remain in. the car.-

ton and are at a temperature substantially-below thatof the new environment, subjecting the plurality of thin-,

walled cans in the carton to induction heating at a frequency of the order of cycles per second for a time sufiicient to raise the temperature of'the thin-walled cans to a value above the dew point of said new environment.

2. The method of claim 1 wherein said induction heating step is performed before any substantial moisture condensation has taken place on the cans in the new environment.

3. The method of claim 1 wherein said carton remains closed during said induction heating step.

4. Themethod of claim 1 wherein the cans are inductively heated to a temperature at-leastas high as that.

of said new environment.

References Cited in the file of this patent UNITED STATES PATENTS,

Segsworth Mar. 2, 1954 a 1 r I l 

